that record your frustration when you hurl the item out the window.) I ask because in celebrating Darwin’s 200th birthday, his work on “intrinsic, universal human expressions” has renewed debates on the semiotics of “two fingers.” Touchpad programmers need to know that there are regional-cultural variants at play here that send signals as different as Churchillian V-for-Victory, “Two pints, please,” and a hostile “Get lost!”

Incidentally, one wonders if Smith Micro, makers of that admirable compression software, realizes that “Stuffit” can be taken the wrong way by uptight Victorians? One such, when told to put his laptop “where the sun don’t shine,” drove it all the way to North Wales.

Returning to the relevance of Buridan’s ass, for those seeking a stronger CS link I can direct you to the real, down-to-earth topic of metastability. In fact, what could be more central to CS than binary ontology: a reminder of Maurice Wilkes’s quip that all computers are analog, and how analog signals beget stable 0s and 1s? At the risk of anthropomorphic (or asinomorphic?) distortion, one imagines baffled states hovering between the equally stable attractors, the piles of straw tagged 0 and 1. If this persists for longer than a clock cycle, we suffer metastability and the system (ass) can surely die. In the vast literature you can read about “the failure of asynchronous sequential logic circuits due to timing problems” (http://www2. computer.org/portal/web/csdl/doi/10.1109/12.391185). You can’t get more CS-speak than that!

My writer’s glut is self-resolving as one topic prompts a reasonable successor.

Consider Nicholas Ourusoff’s letter to CACM ( January 2009) under the banner “CS As Related to Philosophy As It Is to Nature.” This is most encouraging. I have occasionally been chided for “over-waxing philosophically” by those who insist that CS columns should be confined to those vocational bits’n’bytes that govern our daily-breadwinning “project grind.” Yet, we must correct Ourusoff’s belief that computer science, philosophy, and nature are merely “interrelated.” This requires a digression into the meanings of his three elements. Nature, in the broadest sense, is that very “Fabric of Reality” which we aim to comprehend and explain via the tools of science and philosophy. Yet these tools work differently, and they tackle and reveal quite distinct aspects of “reality.”

Briefly (and I recommend the aptly named Philosophy: A Very Short Introduction by Edward Craig, Oxford University Press, 2002), those problems that start as philosophical but gradually succumb to observation, measurement, and experiment, move into the distinct (and really quite recent) domain of inquiry called science. This, essentially,

is what we mean by science. The philosophers continue to debate the essence of unknowability, the ultimate whys and origins and similar unobservables, until, very occasionally, a particular philosophical proposition becomes testable in some objective sense, and moves into the scientific realm. From metaphysics to physics, in fact! A sign of this uneasy and volatile boundary between the two methods can be seen in the now-archaic term natural philosophy. This was used for the physical sciences as recently as my Cambridge days in the 1950s.

In addition to nature and philosophy, Ourusoff’s third element is CS, whereas my discussion involved the general term science. Most people tacitly assume that computer science is a proper, kosher subset of science. The term certainly suggests this, but care is needed. What we call things does not always reflect their meanings in

Most people tacitly
assume that computer
science is a proper,
kosher subset of
science... but care
is needed.

actual usage. The so-called etymological fallacy is often illustrated by names such as pineapple (it’s neither) and Jerusalem artichoke (from elsewhere). Collocations are notoriously misleading. You can’t deduce the meaning of fat cat by looking up its components in a dictionary. Peter Fellgett infamously asked, “Is computer science?”, the rhetoric implying no. I was more cynical in suggesting that “computer science is to science as plumbing is to hydrodynamics.” Similar analogies have been mooted, such as that between Egyptian mensuration and Euclidean geometry: the usefully ad hoc compared with a unified axiomatic system, implying that CS had not yet found a Euclid.